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May-day Mayday....LT1 Serpentine

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
Ok, after several attempts, and about $1,000, my belt is still jumping tracks. The belt is jumping one "rib" or "track" towards the block. It appears to start with the main/balancer, and creep through the system taking the belt one rib backon the pulleys

Has ANYONE ever had this problem on an LT1???

In an attempt to solve the problem, a corvette specialty shop has been through the system as follows:

-Pullies all checked for play, free rotation, and straightness-fine
-Checked pullies with stethascope (sp) to listen to the bearings-fine
-laser sighted the pulleies (had to have balancer and hub machined to make them completly true, and the balacer machined to align it with other pullies as it was sitting almost one rib further forward)-fine now
-bench tested the tensioner, and inspected all of its parts-fine

At this point, it is takes 2 days or less of driving to work (30 mi each way +/-), and what not, to make it jump.

More history: The balancer was replaced in November after a dealer mechanic bent it with a pry bar trying to remove it. Since then, I have been having belts jump. The dealer keeps saying that I need to put a tensioner on (since this would come out of my pocket and not be their fault). When I told them that it was already checked, they say that it should still be replaced, just to eliminate it.

Please help. At this point I feel like dumping the vette, but I could not sell it in good faith with this problem=clasic catch 22.

:(
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
Here it my take on it. Replace the tensioner (either on your own with the G.M. parts receipt, or have the originall dealer do it). Advise them you are doing so one way or another.

If it fixes the problem....then great! If not, you should let them know it will be brought to them on a flatbed with a bill for all the work you have done so far.

I am actually wondering if the balancer could be a defect, or if somehow the center hub is not seated correctly. My only fear would be that they broke off the main crank bolt in the block, or stripped the threads to the point where it won't pull up right. Therefore it flexs/moves under load.

However, 99% of the time it is the tensioner. It either has a hair line crack in the support housing, or it is twisting/bending under a certain load or RPM with the a/c cycle, etc. and jumps the belt.

You could have a hair line fracture in the a/c bracket mount. We had what turned out to be 4 fractures on the 90 vette in the main A/C support bracket. Of course, it was starting to make noise, not just cause belt problems.

What a strange problem. I wish you luck and certainly hope you get it resolved quick.
 
Joined
Jun 20, 2002
Messages
2,509
Location
Tallahassee, FL
Corvette
none right now :(
When does the belt jump off? I had a problem with my '93 during start-up. The car would be running fine, then all of a sudden I would start it up one day, and the belt would half jump off.... I never found the problem, nothing was even touched on the pulley system and the tensioner was fine... fortunately for me it only happened once in a blue moon, a total of maybe 3 or 4 times... I think it may help them diagnose the problem if they know it is upon start-up (if yours is the same as mine was)
 

BigRed

Well-known member
Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
Could it be something like a Alternator or Power steering bracket that is bent slightly?

Just throwing another idea on the table.
 

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
Ok, the dealer who started the problem off is ordering a tensioner (none in the state of Colorado). They are not putting a rush on this. Hence, I will have to wait approx 5 days for the part to materialize.

I am fairly certain that I will be out of pocked for this little exercise. :(

One of the long shots I have heard is that it is the crank. Either the nose of it is bent (not really visable), or that the rear (?) bearing is worn to the point that it is allowing the crank to move when I shift.

HUB- it too was machined because it was not exactly true. They (vette shop) told me that they even checked the end of the crank to make sure that there was nothing hindering proper seating/alignment.

....I am going to buy a horse!
 
D

Drewser

Guest
You will STILL need a mechanic

Do you know what they call an Amish guy with his arm up a horses bum? A mechanic! :upthumbs
(Sorry...I just had to)
 

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
Yeah, but I would have a lot of "giddy-up!"

Besides, when its life is run, it is perfectly acceptable to shoot it.
 

cntrhub

Well-known member
Joined
Jun 17, 2002
Messages
390
Location
North Hollywood, Ca.
Corvette
Miss my '62 & '80 4- Sp. Vettes
Scary

I'd be finding a cushion to put between my knees, and keep them from knocking. Are you going to let the same guy who pried that pulley off with a bar, touch your car again? Open his took box. Make sure he has more that just 30 different length pry bars, and 20 different ounch size hammers!
You want to see the guy's pulley remover/installer tool. The dealer should have one direct from factory. If not, that dealer is not well equipped to work on Vettes, let alone GM products! How about the mechanic? Is his tool money buying cases of beer instead? I've vented enough.
I have two ideas that may or may not pan out? One is to remove the belt. You are going to have to put the car up on a rack or high enough to look under the pulley for optimum viewing. Start the engine for just a few seconds. What you are looking for, is to see the pulley running true, and is not "walking" fore and aft. (I know you said this in your post... check again.) Oh, and guess what.....now is the time to use a pry bar and force the crank (no belt) to walk. Second....since you have the belt off, check the grooves in the pulley. What I mean by this, is to count the V grooves and make sure they have the same amount "matched" as the other pulleys. The new balancer might not be the correct one?
I do not know where everyone starts with belt changes? I begin at the crank and end at the alt. If you are one groove off at any pulley, it will never jump back in place. It tears them up and spits them right off.
Blipping the throttle and watching the tensioner move might tell you if you really need to change that puppy. If it is excessive, then change it. Your problem began, "after the work was finished"...(if you call that work.)
 
F

FordNoMore!

Guest
Pay Your Attorney the 150 buks to write a letter to the first friggin dealer who first started this crap,believe me a letter goes along way,stand in there showroom and demand satisfaction and scream your concernes, it will be heard,I bet U.A little extreme but heck You are out 1k so far because of ther incompitence,My god the outrageous prices they charge in the first place is down right scary,Just to note, I called a dealer for a quote for plug change with cheap gm wires,on 92 vette, I got a quote for 835 buks, ya thats right,the kicker was I called another Dealership in the same city of Vegas and they quoted me 535 buks, 300 buk diff, explain that , and for the gran finale, the dealerships are owned by the same friggin owner,cmon people,give me a break,god I wish some of these owners would call me for repair on there Home A/C unit,hehe....Good luck
 

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
Update

Ok, the dealer tried to get me in to let them look at it again.

Chevy tech/service (whatever you call it) help line:
Called me back and told me the dealer wants to put in a new crank at the tune of $2K. The rep on the phone thought that was a little crazy and is trying to get me to someone else for a second opinion. The Local Service Rep. is whom she is talking to on her side, and he does not like it when the flagship car has this many problems. (another person on my side? I hope)

How much would a new short block cost? I am thinking that if it is the crank, and it is their fault, would it be cheaper for them to put in a new short block rather than tear mine apart.

More to come next week...

ps. ran it at the 1/4 mile track anyway. I had to reset the belt after every run.
 
S

Shadowing1985v

Guest
hmm, here is my 2 cents

when your balancer is not working
and u are flying down the road and its losen it will move back and forth, might make it throw it off. maybe u can just try a smaller belt
 
V

vettepilot

Guest
Let's go all the way back to your first post, and what the Corvette shop did to try to fix your problem.
The first blunder I see is machining the balancer, it is balanced to your crank, that's what those drilled holes are for around the perimeter of the harmonic balancer. Machining probably just disturbed the whole balance. A good engine tech would know that, it's basic mechanics 101.
Second, the prying on the balancer, remember there's a layer of rubber between the outer ring and the inner hub of the harmonic balancer. One should never pry on the outer ring, that's also basic mechanics 101.
If you had no problems before they worked on it, then I doubt you had problems with any of the rotating components after they did the work, sounds like needless machining of your pulleys... sounds more like "blind trouble shooting" to me.
From what you have described I would guess your new harmonic balancer was pressed on a little too deep, if the belt keeps riding back one rib only. OR another possibility, I would also check to see if there are any spacers missing on the accessory mounting brackets, causing the accessories to be slightly forward of the lower pully.
There is where I would start looking. With any luck, the neanderthal who worked on your car didn't beat on the crank too.
I wish you luck on this one.
vettepilot
 

cntrhub

Well-known member
Joined
Jun 17, 2002
Messages
390
Location
North Hollywood, Ca.
Corvette
Miss my '62 & '80 4- Sp. Vettes
Pull the oil filter and dissect it. Pull the paper pleats apart, and look for metal particles. This should tell you if the crank has chewed away any thrust washer bearings or casing. If this is the case, you don't want a short block. You want a "Long Block." No one will take the "time" at a dealership and flush out the particles in the reusable heads and other related engine parts, and do the job right.
The harmonic crank pulleys are so close between each other, that I don't think it will throw off the crank's balance that much. These engines are production built, and don't fall into the category of being "blue printed." You may not feel any difference.
After all, you powered down the 1320 without your fillings falling out of your head. I'm sure the engine runs smooth throughout the rpm range, or else you would have mentioned something about it. You had the new balancer on since November.
The story has gone on from a simple tensioner replacement to now, a new crankshaft? This tells me, there is no solid diagnosis going on at this dealership you've been taking it to.
Pull the oil filter and check for internal damage. You are out a new oil filter and a few quarts of oil with this diagnosis. You have to have a super clean oil drain pan. Drain the oil. Look for micro metallic particles throughout the oil. Drag a magnet through the oil and see if metal is picked up?. Copper/brass filings won't of course, but you can see that contamination in the oil. If the oil filter pleats are clean, and the oil is partical free, you don't need crank work at this point.
Work with the District Manager and not with the dealer you began your trouble with. Let the District Manager call the ball and see how he wants to handle this for you.
 

69MyWay

Well-known member
Joined
Jul 3, 2001
Messages
4,364
Location
Auburndale, Florida
Corvette
1969 Killer Shark
This is getting really strange.

If the crank is bad, there are two possible ways that it could be bad. One, it could be bent on the front snout causing it to rotate in an out of round motion that would disturb the smooth operation of the belt and the idler pulley and possibly toss the belt in the wrong spot. You could possibly bend/distort the snout of the crank by prying/beating on it

HOWEVER*** You would also have a massive front oil seal leak if it was that bent because it would work the seal loose, then sling oil out through the motion on the crank. I doubt the crank is bent.

Second, the thrust portion of the crank in the rear may be worn down, but more likely the bearings would take the worse wear. If they bearings are excessivly worn, I would suggest just dropping the pan and matching a new set of rear bearings to the crank and popping it back together. The bearings are significantly softer than the crank, and will wear first. In fact, on a visual inspection with the crank removed and the main bearing cap that holds the thrust bearings, you can see if they are worn as it will be visibly obvious with dicoloration etc. This would result in the crank being able to walk forward and back in the rotating assembly while also spinning around and around. With your car being a stick shift, from time to time there is more pressure on the forward and back thrust motion of the crank especially if you engine brake to slow down (I do it all the time because I love the way the engine purrrrrrrrrs and pops on the way to a red light).

Again however, if you have that much play in the crank assembly, I would expect other problems to develop fast. I would think there would be an excessive amount of engine "noise" that would keep triggering your knock sensor (as if you were pinging on low octane gas) and retard the timing, thus making that car sluggish as heck.

Eventhough you are going in circles here, I still think it best that you are back where the problem appears to have started from. Just keep good documents and write down the names of all the folks you speak with so you know who told you what when.

If they concluded 100% that the crank is bad, you can easily have that verified by another shop by pulling the dust inspection cover from the flywheel, setting up a feeler gauge, and measuring the amount of forward and aft movement right at the flywheel. If the crank is moving it is moving the same amount at either end, but would be easier to access and measure at the flywheel. You should be able to put a pry bar between the block and flywheel and gently pry and measure the movement. Compare that with the G.M. specs (a little movement is fine). Then, I would set a straight edge on the front pulley from under the car (car on lift) and fire the engine. Watch it run and check the straight edge against the balancer for movement.

Man, I sure would hate to see all this effort still turn out to be a bent or broken power steering or a/c bracket (pried on by the first mechanic).

Please keep us posted.
 
B

Black Ice

Guest
Call your local Chevy Zone office and have all prior repair history paperwork handy. Ross
 

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
I was comming up on an oil change, I guess I pull a filter apart.

I did not know about checking at the flywheel. I will make sure they are 100% before pulling this thing apart any more.

Does anyone know what the size/threads needed to change to a magnetic drain plug?
 

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
Update

Ok, The vette is at the dealership that the Area Service Rep suggested. (Oddly enough, this dealership is owned by the say guy that owns the dealership that messed up my vette)

They think that the tensioner pulley is to blame. They believe that somehow it wore in such a way as to allow the belt to "walK" or creep up and off. (Of course, the fact that it jumps off the balancer first would tend weaken that theory, but oh well.)

I will be getting it back tomorrow afternoon. Anyone want to take bets on how long it will take for the belt to jump?

Another dealer (in San Diego) suggested something else. After talking with him on the phone about the problem and all the history, he thought it might be the crank. He suggested that it might have excessive end play possibly due to the first wrench brain using a pry-bar on the balancer.

I miss my vette.:cry
 

BigRed

Well-known member
Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
I may have missed it in another post but since your car is a standard, could a thrust bearing be worn causing the crank to move?

When my friend bought his 70' GTO the motor was out from purchase (We had to put it in) but we found that the crank had a hundrend ten thousand endplay!! turned out the thrust bearing had been shot for a LONG time and soon the other bearings got weak and eventually the crank was scored permanently. (Block and mains were fine thank god.) So after a new crank/bearing it was perfect.

If this is your problem (I sure hope not) get it addressed SOON, another system that got shot through his motor was the connecting rods for the pistons which would have led to REAL problems. (Again the block was not harmed WOOT!)

So If its not this,and the brackets for the ALT/PWR steering are not bent, could it be a bearing in another piece? And this may sound stupid but could it be the Clutch on the A/C? If thats jammed could it not throw the belt?
 

Topless

Well-known member
Joined
Nov 12, 2001
Messages
444
Location
San Diego, CA
Corvette
1992 Convt w/hard top; 2004 Z06 Z16; 1962 327/300
The A/C pulley has been checked, and eliminated. (So much for the easy/inexpensive)

I am guessing a crank, but the dealer that would have to shell out for it will probably not agree. If for nothing else than the fact that I will be making them pay for it.

The thrust bearing is also a possibility. I need to find out tomorrow what the end play is. If they have done it correctly, they should be able to tell me what the movement is, and what it should be.

BTW, when I asked the dealer in San Diego what the remedy would be IF it was the crank...he said a new engine. As long as Chevy is paying for it, any reason not to?

-Mike
 

BigRed

Well-known member
Joined
May 23, 2001
Messages
948
Location
Edmonton
Corvette
1985 Bright Red Rocket
Any mods? then Nope! :L My dad bought a early Grand Cherokee (93) with the 4.0 liter I-6 They tried aluminum heads on the cast block w/o sleeves for the pistons.

After awhile it knocked and knocked worse, they simply replaced the motor at 50 000Km's He was laughing, the vehicle was just off warranty and then on the motor they had to give him another 35 000. Chrysler wasn't impressed with that recall LOL

So anyway if they do replace the motor you SHOULD end up with a engine warranty right from GM... BONUS!
 

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